Electric lamp



June 13, 1967 R. A. J. M. MEIJER ETAL 3,325,665

ELECTRI C LAMP Filed July 5, 1963 III FIG.5

FIGA

United States Patent C) 3,325,665 ELECTRIC LAMP Riksterus Auguste Johannes lvlaria Meijer and Leo Henricus Verheeh, Eindhoven, Netherlands, assignors to North American ihilips Company, Inc, New York, N.Y., a corporation of Delaware Filed July 5, 1963, Ser. No. 293,009

Claims priority, application Netherlands, Italy 6, 1962,

2 Claims. (Cl. 313-113) Our invention relates to an electric lamp and, in particular, to a lamp having an iodine containing gas filling and a filament wound entirely or partially into a helix and provided with one or more terminal members sealed in a base or pinch therein.

With suitable proportioning and suitably chosen operating conditions the presence of a small amount of iodine in the free or combined state in such a lamp produces the so-called iodine circulation. This results in that any tungsten of the filament which has vaporized and found its Way onto the wall of the bulb is returned to the filament which has two important advantages. First, there is comparatively little blackening of the bulb; and second, the filament is regenerated by the tungsten returned during operation of the lamp. Consequently, in lamps of this kind a filament of comparatively high power can be accommodated in a comparatively small bulb, While the life of the lamp can be made comparatively long.

The temperature distribution in such a lamp plays a decisive part in the production of a satisfactory iodine circulation. Especially, contact of the iodine with metals liable to be adversely affected by it should be avoided, since this may detract from the life of the lamp.

A principal object of our invention is to provide a lamp having a gas-filling containing iodine which is of simplified construction in which the metal parts are relatively resistant to the action of molecular iodine in various temperature ranges.

A further object of our invention is to provide a lamp of the aforesaid type in which the li ht distribution is such that only light from the central portion of the filament is transmitted through the envelope.

In a lamp according to the invention, each of the ends of the filament extends in a base support or in the envelope pinch in which it is secured to a terminal member sealed therein. Further, in accordance with the invention, the lamp is provided, at least in the proximity of the part of the filament adjacent a pinch, with means which in the operation of the lamp prevent that part of the filament from radiating light to the space surrounding the lamp, at least on part of the periphery of the lamp envelope extending at right angles to the lamp axis.

Thus, unlike the usual construction of an iodine-filament lamp, in the lamp in accordance with the invention the end of the filament extends into the base or pinch and there is Secured to the terminal member sealed therein. As a result, it is not necessary to arrange within the lamp space component parts consisting of other metals which at certain temperatures cannot satisfactorily withstand the action of iodine and the additional advantage is obtained that the manufacture of the lamp is simplified. The metal parts required for a lamp having one filament comprise, in addition to this filament, only two terminal members sealed in the base and two external current supply wires so that a total of four joints are sufficient.

However, the fact that the filament extends into the base or pinch in some applications has the disadvantage that in the operation of the lam the filament radiates light throughout its entire length, that is to say from the boundary face of a pinch to the boundary face of a pinch. If such a lamp is to be used to produce a sharply defined beam, this phenomenon may be troublesom which is obviated by providim the lamp with the above mention d means which prevent light from being radiatel to certain tarts of the space surrounding the lamp.

In one embodiment of the lamp in accordance wit the invention the lamp envelope is rendered impermeabl to light at the portion in close proximity to the base.

In another embodiment the lamp is provided with screen which may be external to the envelope in 0105 proximity to the base for preventing the transmission 0 light through the portion of the envelope adjoining th pinch. This screen may be external to the lamp. In orde to avoid damage to the screen when in use, however, i is of advantage to accommodate the screen, which pref erably is made of platinum, within the bulb. Platinum i capable of withstanding the action of atomic ant molecular iodine.

In a further embodiment of very simple construction the end of the filament which extends into the pinch i; surrounded by a tube-shaped member, which may be wire of tungsten wound into a helix. Such a tube-shape member generally results in that the portion of the fila ment surrounded by it is only slightly visible, so that th light which may be radiated by this portion is effectivelj screened by the tube-shaped member. When the tube shaped member is in contact with the portion of a fila ment it surrounds, the temperature of this portion of tilt filament falls to a temperature such that it emits substan tially no light.

In an embodiment of the lamp in accordance with tht invention in which the bulb is made of glass, more particularly hard glass, the tube-shaped member may extent into the pinch almost up to the terminal member. It has been found that the likelihood of the pinch cracking is greatly reduced by this construction.

The lamp in accordance with the invention is partic' ularly advantageous when combined with a substantially parabolic reflector. In this case the lamp is arranged sc that its filament, which is at least partially Wound intc a helix and extends in a straight line, extends along 01 parallel to the axis of the reflector in the reflector space. while a portion of the filament coincides with or is adjacent to the focus of the reflector. According to the invcn tion in this case, the lamp is further disposed so that the portion of the filament situated between the apex and the focus of the reflector is provided with means which prevent this portion from radiating light to the space surrounding the lamp, at least over that portion of the lamp envelope extending at right angles to the lamp axis.

The invention will now be described with reference t( the accompanying drawing, in which:

FIG. 1 shows one embodiment in section of the lam; in accordance with the invention;

FIGS. 2 and 3 show a second embodiment of the 1am; in accordance with the invention, FIG. 3 being a cross sectional view of the lamp taken through the plane III-- III of FIG. 2;

FIGS. 4 and 5 show a third embodiment of the lam; in accordance with the invention, FIG. 5 being a cross sectional view of the lamp taken through the plane Vv of FIG. 4;

FIG. 6 shows a combination of a parabolic reflector and the lamp of FIG. 2.

The lamp shown in FIG. 1 has a tubular envelope 1 which at both ends terminate in flat pinches 2 and 3, respectively, in which the ends of the filament 4 are sealed Filament 4 comprises a central helically wound portior 4a the ends of which terminate in straight portions 4L and 4c. The portions 4b and 40 project through boundary faces 5 and 6 of the envelope 1 so as to be partly disposed in the pinches 2 and 3 respectively. These filament portions are each secured to a terminal member in the form oi ires 7 and 8, respectively, of greater diameter. At their iter ends the wires 7 and S are joined to nickel currentlpply wires 9 and 10 respectively. Bulb 1 is provided with.

sealed-otf exhaust tube which is arranged asymmetriilly with respect to the remainder of the bulb to prevent. ilse reflection. The bulb contains a filling gas, e.g. kryp- I11 and iodine in the free or combined state in an amount: ich that when the lamp is operated, so-called iodine cirnation is produced in the bulb. As has been menoned hereinbefore, this reduces blackening of the bulb ad has a regenerating effect on the filament.

Because filament 4 extends from terminal member 7 to :rminal member 8, a very simple lamp construction is. btained. In certain cases it may be considered a disdvantage that in the operation of the lamp not only 1e helically wound portion 4a of the filament 4 but also s ends 4!) and 4c, insofar as they lie Within the boundary ices 5 and 6 of the bulb 1, emit light. In the lamp shown. 1 FIG. 1 this disadvantage is obviated by providing each. f the ends 1a and 1b of the bulb 1 over a length which is: ubstantially equal to the length of the ends 417 and 40' f the filament 4 respectively, insofar as these ends are ituated between the surfaces 5 and 6, with a layer which 5 impermeable to light and for the sake of clarity is hown by shading in the figure. This results in that he light issuing from the lamp is emitted substantially nly by the helically wound portion 4a of the filament; nd only leaves the bulb through the clear part thereof ncircling this portion.

In the embodiment shown in FIGS. 2 and 3 another onstruction for preventing the radiation of undesired ight is used. A slightly curved screen 24 of platinum .rranged in the bulb space 25 is secured by means of a bin platinum wire 23 to a terminal member 21 which is. ncorporated in the left-hand pinch 22 and has the shape: if a foil of molybdenum. The screen extends longitudinally hrough a distance which is about equal to the length if the straight portion 26b of a filament 26 extending in be space 25. Otherwise the construction of the lamp .hoWn in FIG. 2 is similar to that of the lamp shown in FIG. 1. The only further differences are that unlike hose of FIG. 1 the terminal members 21 and 27 have he form of foils, and that only one of the straight ends )f the filament 26 is screened.

As is shown particularly by FIG. 3, the screen 24 :xtends at right angles to the longitudinal axis of the lamp and through an angle a with respect to the peripheral lirection of the lamp. Consequently, if FIG. 2 shows the operating position of the lamp, the straight filament and 26b will only be prevented from radiating light into the space surrounding the lamp in the upward direction through the angle a.

The embodiment shown in FIG. 4 uses a filament which is helically wound and has a portion 40a which is intended for the emission of light and is shaped substantially in the form of a V. In this embodiment also the straight filament ends 4617 and 400 extend into a common pinch 41. In this pinch they are secured to terminal members 42 and 43 in the form of pieces of thicker molybdenum wire to which current-supply wires 44 and 45 of nickel are secured. Bulb 46 is provided with a sealed-01f exhaust tube 47.

In this embodiment, in order to prevent the straight filament ends 40b and 40c from radiating light, these ends are surrounded by sheath-shaped members 48 and 49 which each comprise a helically wound tungsten wire. These members surround the straight filament ends 4% and 400 with a small amount of clearance. Any light emitted by the straight filament ends 4% and 4110 is rendered invisible by these sheath-shaped members so that only the helical portion 40a of the filament radiates light. The bulb of this lamp is made of hard glass. The fact that the sheath-shaped members extend into the pinch 41 provides the additional advantage that in the operation of the lamp the hard-glass pinch is less likely to crack than if the straight filament ends 40b and 400 were directly sealed in the hard glass.

FIGURE 6 shows diagrammatically a substantially parabolic reflector 61, the optical axis of which is designated X-X. At the rear this reflector has an aperture 62 for the introduction of a source of light. A plate-shaped holder 63, on which a lamp 66 of the type shown in FIG. 2 is mounted by means of rigid current-supply wires 64 and 65, fits within this aperture. When the holder is arranged in the reflector, the longitudinal axis of a filament 67 coincides with the optical axis X-X of the reflector 61. The focus F of the reflector lies in this axis X-X. The filament 67 is preferably arranged so with respect to the focus F that the rearmost turn of the helical portion 67a of this filament coincides with the focus F. If now the straight end 6711 of the filament 6-7, which end is near the apex of the reflector, is screened upwardly by a screen 68 arranged in the lamp 66, it is ensured that the upper half of the reflector 61 produces no light ray which is at an upwardly directed angle to the reflector axis X-X.

In the arrangement shown, the lower half of the reflector can produce upwardly directed light rays. If this is troublesome, it may be obviated, for example, by shifting the focus of the lower half of the reflector towards the aperture thereof with respect to F.

While we have described our invention with reference to specific examples and embodiments thereof, other modifications will be readily apparent to those skilled in this art without departing from the spirit and scope thereof as defined in the appended claims.

What we claim is:

1. A source of illumination comprising a light-transmissible envelope filled with an iodine-containing gas, an helically-wound filament provided with straight end portions and adapted to glow upon the passage of an electrical current therethrough and positioned within said envelope, a base support within said envelope into which at least one straight end portion of said filament extends, a terminal member sealed within said base support to which the end of said filament is connected, and a relatively light-impervious screen member constituted of platinum and positioned to intercept light only radiated by said straight end portion of said filament extending into said base support.

2. A source of illumination as claimed in claim 1 wherein said screen is a sheath-shaped member of helically-wound tungsten wire surrounding the portion of said filament extending into said base support.

References Cited UNITED STATES PATENTS 1,409,469 3/1922 Reece 313-117 X 1,445,398 2/1923 Kambayashi 313-219 1,807,140 5/1931 Vonwedel 240-4125 2,006,839 7/1935 Moller 240-4125 3,132,278 5/1964 Collin et al. 313-200 X FOREIGN PATENTS 10,284 5/ 1896 Great Britain. 321,237 9/ 1934 Italy.

JOHN \V. HUCKERT, Primary Examiner.

A. J. JAMES, Assistant Examiner, 

1. A SOURCE OF ILLUMINATION COMPRISING A LIGHT-TRANSMISSIBLE ENVELOPE FILLED WITH AN IODINE-CONTAINING GAS, AN HELICALLY-WOUND FILAMENT PROVIDED WITH STRAIGHT END PORTIONS AND ADAPTED TO GLOW UPON THE PASSAGE OF AN ELECTRICAL CURRENT THERETHROUGH AND POSITIONED WITHIN SAID ENVELOPE, A BASE SUPPORT WITHIN SAID ENVELOPE INTO WHICH AT LEAST ONE STRAIGHT END PORTION OF SAID FILAMENT EXTENDS, A TERMINAL MEMBER SEALED WITHIN SAID BASE SUPPORT TO 